Spring 2015 Benha University Faculty of Engineering at Shoubra ECE-322 Electronic Circuits (B) Lecture #1 Course Introduction and Differential Amplifiers Instructor: Dr. Ahmad El-Banna
Agenda Course Objectives Course Information Lectures List Elec. Cts B, Lec#1, Spring 2015 Differential Amplifiers 2
Course Objectives Understand the basics of differential and operational amplifiers. Study the different circuits of Op-Amp. Learn the concept and different types of Active filters. Explore the signals generators and voltage regulators. Study the Phase Locked Loop (PLL) circuits. Usage of CAD packages in designing and analyzing the electronic circuits. 3
Course Information Instructor: Dr. Ahmad El-Banna http://bu.edu.eg/staff/ahmad.elbanna Office: Room #305 Email: ahmad.elbanna@feng.bu.edu.eg ahmad.elbanna@ejust.edu.eg Lectures: Wednesday: 11:15-14:00 Prerequisite: ECE-312 Office Hours: Tuesday (12:00~15:30) & Wednesday (14:00~16:30) & Thursday(11:00~14:30) T.A.: Eng. Mohamed Ismail Texts/Notes: Lectures slides, available by each lecture, and found online at http://bu.edu.eg/staff/ahmad.elbanna-courses/12135 T. Floyd, Electronic devices - Conventional Current Version, 9 th edition, Prentice Hall. R. Boylestad, Electronic Devices and Circuit Theory, 11 th edition, Prentice Hall. 4
Course Information.. Additional References: Sedra & Smith, Microelectronic Circuits, 6 th edition. Horowitz & Hill, The Art of Electronics, 2 nd edition, Cambridge Press. EE113 Course Notes Electronic Circuits by Prof. G. Kovacs, Stanford University, Department of Electrical Engineering. Credit: 150 Marks Grading: 90 Marks Final Exam (Closed-Book) 30 Marks Mid Term Exam (Open-Book) (10) Quizzes and Homework (10) Tutorials Activities (10) 30 Marks Individual Project (10) Group Project (10) Oral Exam (10) 5
Lectures List Week#1 Week#2:5 Week#6 Week#7 Week#8:10 Week#11 Week#12:13 Week#14 Introduction and Differential Amplifiers Op-AMP Basics and Circuits Active Filters Mid-Term Exam Signals Generators & Voltage Regulators PLL Circuits Introduction to VHDL Oral Exam and Project Delivery 6
DIFFERENTIAL AMPLIFIERS 7
Basic Internal Arrangement of an Op-Amp. Stage#1 Differential Amplifier 8
Single-Ended Input & Double-Ended (Differential) Input 9
Double-Ended Output 10
Common Mode Operation Ideally, the two inputs are equally amplified, and since they result in oppositepolarity signals at the output, these signals cancel, resulting in 0-V output. Practically, a small output signal will result. Common-Mode Rejection Noise (any unwanted input signal) is generally common to both inputs, the differential connection tends to provide attenuation of this unwanted input while providing an amplified output of the difference signal applied to the inputs. This operating feature is referred to as common-mode rejection. 11
Differential Amplifier Circuit Input signal combinations: Single-ended : If an input signal is applied to either input with the other input connected to ground. Double-ended: If two opposite-polarity input signals are applied. Common-mode : If the same input is applied to both inputs. 12
DC Biasing With ac inputs obtained from voltage sources, the dc voltage at each input is essentially connected to 0 V. The two transistors are matched. 13
AC Operation 1- Single-Ended AC Voltage Gain 14 R E very large (ideally infinite) ac voltage gain magnitude
AC Operation.. 2- Double-Ended AC Voltage Gain A similar analysis can be used to show that for the condition of signals applied to both inputs, the differential voltage gain magnitude is: H.W. Derive the A d equation 15
Common Mode Operation 16
Use of Constant-Current Source A good differential amplifier has a very large difference gain A d, which is much larger than the common-mode gain A c. The common-mode rejection ability of the circuit can be considerably improved by making the common-mode gain as small as possible (ideally, 0) The larger R E, the smaller is A c. One popular method for increasing the ac value of R E is using a constantcurrent source circuit. 17
For more details, refer to: Chapter 10, R. Boylestad, Electronic Devices and Circuit Theory, 11 th edition, Prentice Hall. The lecture is available online at: http://bu.edu.eg/staff/ahmad.elbanna-courses/12135 For inquires, send to: ahmad.elbanna@feng.bu.edu.eg 18